CLASSIFICATION. 65! 



higher order of relationship, where the limits are broader than in 

 the genus. Genera which are thus related make up the family. 

 In the case of these genera the family has been named after the 

 lily, and is the lily family, or LiliacecB. 



1139. Order, class, group. In like manner the lily family, 

 the iris family, the amaryllis family, and others which show 

 characters of close relationship are united into an order which 

 has broader limits than the family. This order is the lily order, 

 or order Liliales. The various orders unite to make up the class, 

 and the classes unite to form a group. 



1140. Variations in usage of the terms class, order, etc. 

 Thus, according to the system of classification adopted by some, 

 the angiosperms form a group. The group angiosperms is then 

 divided into two classes, the monocotyledones and dicotyledones . 

 (It should be remembered that all systematists do not agree in 

 assigning the same grade and limits to the classes, subclasses, 

 etc. For example, some treat of the angiosperms as a class, 

 and the monocotyledons and dicotyledons as subclasses; while 

 others would divide the monocotyledons and dicotyledons into 

 classes, instead of treating each one as a class or as a subclass. 

 Systematists differ also in usage as to the termination of the 

 ordinal name; for 'example, some use the word Liliales for Lilii- 

 flora, in writing of the order.) 



1141. Monocotyledones. In the monocotyledons there is a 

 single cotyledon on the embryo; the leaves are parallel veined; 

 the parts of the flower are usually in threes; endosperm is usu- 

 ally present in the seed; the vascular bundles are usually closed, 

 and are scattered irregularly through the stem as shown by a 

 cross-section of the stem of a palm (fig. 539), or by the arrange- 

 ment of the bundles in the corn stem (fig. 57). Thus a single 

 character is not sufficient to show relationship in the class (nor 

 is it in orders, nor in many of the lower grades), but one must 

 use the sum of several important characters. 



1142. Dicotyledones. In the dicotyledons there are two 

 cotyledons on the embryo; the venation of the leaves is reticu- 

 late ; the endosperm is usually absent in the seed ; the parts of the 



